Simplify the following expression: $n = \dfrac{2}{7y} + \dfrac{7}{3y}$
Answer: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $7y$ and $3y$ $\lcm(7y, 3y) = 21y$ $ n = \dfrac{3}{3} \cdot \dfrac{2}{7y} + \dfrac{7}{7} \cdot \dfrac{7}{3y} $ $n = \dfrac{6}{21y} + \dfrac{49}{21y}$ $n = \dfrac{6 +49}{21y}$ $n = \dfrac{55}{21y}$